It is historically illiterate. Doubtful the USSR would have prevailed if Nazi Germany could have put all of their resources on the Eastern Front.
That depends on a number of factors and even that would likely be an oversimplification.
1) What are the Western Allies (particularly the US) doing? Are we still providing Lend-Lease? It's actually pretty well-documented that the backbone of Soviet logistics was built on American (particularly Studebaker) trucks and vehicles. A significant portion of the VVS (Soviet Air Force) was using American built planes (particularly the P-39 Airacobra). There were even Soviet tank divisions equipped entirely with Shermans.
If the Western Allies aren't in this particular area, the Eastern Front becomes bloodier and potentially Leningrad/Moscow/Stalingrad might have a different outcome initially but if the other options stay the same, the ultimate outcome remains the same.
2) Is Barbarossa launched on time or is delayed like it was in reality? Had Barbarossa been launched one month earlier it would've caught the Soviet Red Army in the midst of Stalinist purges and major reorganizations instead of the aftermath which left a lot of more competent commanders such as Chuikov. This chaos would likely have led to faster and further advances before the winter of 1941 set in.
If the advances are fast enough to prevent Soviet industry from relocating core and essential industries (firearms, munitions, tanks, etc.) to the Ural Mountains maybe a different outcome could be achieved in theory.
3) Are the Germans continuing to run their existent command and control structures and doctrines? The Germans were very inflexible and often suffered infighting at the operational level. While individual squads and platoons may have demonstrated significant cohesion and organization to accomplish their objectives, the higher up in scale you go the less organized and built for purpose the Wehrmacht becomes. Operational maneuvers above that of a single Corps were more or less tied to Der Fuhrer's approval which made Wehrmacht advances or retreats very haphazard and contradictory. This is especially demonstrated at Stalingrad and later Kursk because the Germans basically had no clue what their objective was, their goal, their purpose beyond "killing Soviets". Operational indecision and the slow approval process for major movements from Der Fuhrer meant the Germans could never adapt or react to the Soviets in any meaningful way long term. Entire offensives German and Soviet were decided early on precisely because of these problems.
Contrast that to the Soviets. At the squad/platoon level, the average Soviet conscript unit looked by appearances little different than a charging rabble. But the higher up the command and control scheme you went the more organized and more chillingly clearer in purpose they became. At the operational level, entire army groups knew exactly when and where they were supposed to be and what they were intended to do. This then filtered down the chain of command to individual units who were given all the information they needed to achieve their specific objectives. Everything moved and placed to support each other part of the grand operation as a whole. An infantry company moves to take a village which ends up supporting the flank of a tank battalion which breaks the main line allowing artillery to move their fire onto new targets.
One time of this was best demonstrated at the Vistula-Oder Offensive in what would become later known as Soviet "deep battle" doctrine. Swift advances, simple orders, known but flexible timetables deciding various outcomes. On the ground it might've looked little different than a horde of men and tanks coming at you, but step back and look at the entire theater of operations and it's terrifying how clear and precise their aims and purpose is. And it worked, Vistula-Oder was a horrifically damaging blow to the Germans that more or less broke the back of the Eastern Front once and for all and led to the rapid advances into the remander of Poland and eastern Germany that ended the war.
4) What's the political situation in an isolated Eastern Front? Are the Western Allies supporting Stalin and the Soviets politically? Is Stalin (or Hitler) allowed to remain in power or will there be assassination/decapitation strikes to try and change that? Are the Wehrmacht behaving in such a way they continue to be seen as liberators instead of becoming subjugators?
If the Allies withdraw political (and presumably equipment) support a different outcome is possible, especially if Barbarossa is launched on time. If Hitler is removed from the equation, does Germany get somebody much better in terms of military competence? Similar for Stalin, if he gets removed does the Soviet Union get a weaker or stronger leader that follows? If the Wehrmacht had behaved differently occupying former Soviet territories they may have drawn on a wide pool of manpower and support against the Soviets as indeed initially in places like Ukraine where they had had quite a bit of famine and other problems in the 1930s under Soviet rule they were seen as liberators against the Communists. (Remember the Russian Civil War hadn't even been over for 20 years at that point.) But instead they behaved as subjugators, practicing genocide or at least indifference to the civilian populace which turned the opinions of folks inside occupied territories from liberators to enemies that must be driven out. As much as Ukrainians hated the Russians, by 1943 they hated the Germans worse such that it was a better proposition to go back to being Red than becoming Dead with the Nazis.
So many factors that could've led to mildly or even completely different outcomes, all in the absence of us doing a lot of things.
It is also lame considering the USSR was not fighting the Nazis in Africa and Italy let alone doing jack shit about Japan.
There's a reason why you know. The last thing the Western Allies wanted to do was spread the Soviets too thin by trying to go against Japan in Manchuria and they were surrounded by neutral states in the Middle East (particularly Turkey) that wouldn't let them march troops to British bases and thus sent to North Africa. They needed every last Soviet conscript in Soviet territory tying up as much men, materiel and otherwise from the Germans so that the Western Allies could counter the machinations of Germany and Italy in North Africa, the Mediterranean and elsewhere.
Remember in 1941 the British Empire was effectively beat to shit militarily and the US wasn't yet in the war. In 1942, the US had the bulk of the US Navy off in the Pacific fighting Japan as well as the Marine Corps. We were too depleted or extended to risk operations to bring Soviet troops to North Africa and elsewhere. We needed them right where they were.
All the USSR was doing was defending their own homeland after being double-crossed by their former ally. While Americans, British, Canadians, Aussies, Kiwis were sacrificing their soldiers to liberate other countries thousands of miles from home.
We had territories (particularly the Philippines and other Pacific islands) under attack too by the Japanese. We even had a significant battle on US soil in Alaska at Attu Island. The British Empire was under attack worldwide and the French possessions were being taken to task to break away from the Vichy and fold into the Free French Forces.
Likewise a number of the possessions under attack were either US, Dutch, British or Commonwealth (Australia, India, etc.). We had to defend and liberate them for better positioning to further attack the Axis worldwide. At our best in the 1940s we could not possibly simply sail a fleet into Japan and march troops on Tokyo. We needed bases to move support from bombers to naval bases to barracks and hospitals, Hawaii was too far away and the Philippines were held by the Japanese. Likewise we could not possibly have attempted a landing in Germany. We needed bases in Britain and we needed our flanks secure from reinforcements out of Italy or North Africa. North Africa was used as a base and springboard for our moves into Italy, we could not have sailed from Chesapeake Bay to Sicily. We needed air support based in North Africa, we needed secure bases to move ships and supplies to Gibraltar, Malta and more.
In shortest terms, we liberated those territories because they helped our overall mission against Germany, Italy and Japan. We didn't do it out of the kindness of our hearts or some kind of obligation to the European Allies. Similarly we needed the Soviets to throw every last effort they had on the Eastern Front to help the overall mission.